The present invention relates to a process for presulfurizing a hydrocarbon treatment catalyst and/or preconditioning a catalyst to be presulfurized.
It is often preferable to sulfurize metal components of some refining and/or hydrocarbon hydroconversion catalysts. Such "presulfuration" is carried out either when the catalysts are new or when they are regenerated prior to reuse.
Presulfuration is desirable when using refining reactions, for example, the desulfuration or hydrodesulfuration of such gasolines, as catalytic cracking or steam cracking gasolines, the sulfur content of which should be reduced before their use, with the octane number of these gasolines being unmodified, or modified as little as possible. Such desulfuration reactions are generally performed in the presence of hydrogen at between 200.degree. and 400.degree. C., under a pressure, for example, of from 5 to 60 bars, with a space velocity (expressed in m.sup.3 of injected liquid feedstock per m.sup.3 of catalyst per hour) of from 0.5 to 15, with a hydrogen partial pressure of from 4 to 60 bars. The feedstock is, for example, a gasoline generally distilling at between 30.degree. and 220.degree. C., with a bromine number of from 40 to 80 (g/100 g), comprising from about 15 to 45% by volume of olefins (essentially mono-olefins or minor amounts of diolefins) and from 15 to 25% of aromatic hydrocarbons.
The catalyst which is used for this type of desulfuration or hydrodesulfuration generally contains a non-acid support, for example, an alumina or alumina mixtures (U.S. Pat. No. 4,334,982), or any other appropriate support with at least one metal or metalloid oxide base such as magnesia (U.S. Pat. Nos. 4,132,632, and 4,140,626), silica, silica-aluminas, silica-magnesias, fluorinated silicas, boronic aluminas, clays, coals, fluorinated aluminas). These support mixtures appear at least partially in non-crystalline or crystallized form (zeolites). The catalyst also comprises from about 0.2 to 30% of at least one active metal selected from groups VI, VIII, or any other active metal, for example, from the group consisting of cobalt, molybdenum, nickel and tungsten (U.S. Pat. No. 3,732,155 and 3,804,748). A combination of two of these metals is generally used, for example cobalt-molybdenum, nickel-molybdenum, cobalt-tungsten, tungsten-molybdenum, cobalt-nickel, or nickel-tungsten couple. It is also possible to use, for example, a noble metal of group VIII from the platinum family such as platinum or palladium (U.S. Pat. No. 4,098,682).
Thus, in the prior art, the new or regenerated catalyst is generally subjected, before use, to presulfuration, which is achieved in the hydrodesulfuration reactor. By this process, the catalyst includes for example about 50 to 110% of the stoichiometric amount of sulfur calculated according to the metals present as follows: EQU Co.sub.9 S.sub.8, MoS.sub.2, WS.sub.2 and Ni.sub.3 S.sub.2.
In the prior art, presulfuration is achieved at a temperature greater than or equal to 180.degree. C. and particularly 250.degree. C.) the reaction temperature chosen for the hydrodesulfuration reaction, over several hours, by means of a hydrogen sulfide mixture which is generally diluted in hydrogen about 0.5 to 5% by volume), at an appropriate space velocity of from 1,000 to 3,000 liters of gas under normal temperature and pressure conditions per liter of catalyst per hour (U.S. Pat. No. 4,334,982). The presulfuration proper can be achieved stepwise with respect to temperature (French Patent No. 2,476,118). Various sulfurizing agents other than hydrogen sulfide H.sub.2 S), for example, a sulfur compound from the mercaptan series can be used, as well as carbon bisulfide (CS.sub.2), other bisulfides, various disulfides, thiophenic compounds and preferably dimethylsulfide (DMS) and dimethyldisulfides (DMDS).
It is also better to sulfurize (presulfurize) a regenerated catalyst for hydrocarbon hydroreforming reactions (especially naphtha reforming) and aromatic hydrocarbon production reactions (aromizing), for example, for producing benzene, toluene and xylenes (ortho, meta or para), either from saturated or unsaturated (for example, pyrolysis, cracking, and particularly steam cracking or catalytic reforming gasolines) or from naphthenic hydrocarbons which can be converted into aromatic hydrocarbons through dehydrogenation.
These reactions are the generally performed at an average temperature of between 400.degree. and 600.degree. C., a pressure of from 1 to 60 bars, an hourly velocity of from 0.1 to 10 volumes of liquid naphtha per volume of catalyst, and at a recycle ratio of 0.5 to 20 moles of hydrogen per mole of feedstock.
The catalyst can, for example, contain at least one noble metal from the platinum series, (i.e., platinum, palladium, iridium, rhodium, ruthenium, or osmium), deposited on an appropriate support (i.e., alumina, silica, silica-alumina, fluorinated aluminas, fluorinated silicas, zeolites, or a combination thereof in an amount of between 0.1 and 5% by weight in relation to the catalyst. The catalyst can also contain at least one halogen (chlorine, fluorine, etc.) in a weight proportion of 0 to 15%.
Optionally, catalyst can also comprise at least one promoter metal in a weight promoter metals include those from groups VIII, VI A and VI B, I B and II B, III A, IV A, V A and V B, IV B, III B, I A and I B metals of the lanthanide series; and the noble and non-noble metals of group VII, particulating copper, silver, gold, germanium, tin, indium, thallium, manganese, rhenium, tungsten, molybdenum, niobium, and titanium.
In these catalytic reforming or aromatic hydrocarbon production reactions, sulfuration of the new or regenerated catalyst is accompanied by catalyst hydrogen reduction and is achieved in or near reactor head. The temperature in the sulfuration zone depends on the reduction temperature, which generally ranges from 480.degree. to 600.degree. C. However, although efficient, in situ sulfuration is a difficult and tedious process to implement U.S. Pat. No. 4,172,027).
Prior art sulfurizing agents include hydrogen sulfide, either pure or diluted with diluted with hydrogen or gaseous hydrocarbons; dimethyldisulfides diluted with hydrogen; or other sulfur compounds such as alkylsulfides or alkylmercaptans diluted with hydrogen. The pressure is the same as that inside the reforming reactor or the aromatic hydrocarbon production reactor. The reaction duration ranges from minutes to days, depending on the operating conditions (see U.S. Pat. No. 4,172,027).
In some cases, presulfuration of a new or regenerated catalyst is desirable for the partial or total sulfuration of a catalyst having as a base one of the previously mentioned supports and at least one of the previously mentioned active metals, for use in such hydrocarbon conversion reactions such as reactions of hydrogenation, dehydrogenation, alkylation, hydroalkylation, dealkylation, hydrodealkylation, steam dealkylation, isomerization, and hydrodemetallization of heavy feedstocks.
When necessary, the sulfuration or presulfuration process can be advantageously carried out according to one of the above-described prior art techniques.
The catalyst metals employed in refining, hydrorefining or petrochemistry, whether new or regenerated, are most often used in oxidized for and sometimes in metallic form (especially in the case of certain reforming catalyst metals). Since the metals of these catalysts, are often active only in sulfide or partial sulfide form, they must be subjected to a catalyst sulfuration prior to use.
Because the catalyst regeneration process is increasingly being performed by specialists, sometimes far away from the industrial site, it is more productive to give the provide refineries with a ready-to-use product. This is now possible using the process of European Patent No. 84,400,234. In this process, a sulfur compound is incorporated into the catalytic mass, causing sulfuration or presulfuration of the catalyst when said catalyst is subsequently contacted with hydrogen in or near the reaction zone (feedstock treatment zone) of course, the sulfur compound can also be incorporated in the vicinity of the industrial unit at the catalyst treatment site, or off-site on a new or a regenerated catalyst before it is used in the industrial unit.
More precisely, in European Patent No. 84,400,234, the catalyst sulfuration process is characterized by a preliminary stage in which the sulfur compound is incorporated into the catalytic mass.
This preliminary incorporation stage (called pretreatment in situ or ex situ, depending on whether it is performed near or away from the industrial unit, e.g., at the catalyst regeneration or manufacturing site, need no longer be carried out next to the reactor i.e. at the reactor head or in zones in more or less direct communication with the reactors. As a result, the sulfur incorporation process need not depend on operating conditions (e.g., temperature, pressure, etc.) extant the reactors themselves or in annexes to these reactors (for example, the catalyst preliminary hydrogenation zone).
Subjecting the catalyst from the outset preferably to an activation reaction in the presence of hydrogen (generally over 100.degree. C.), the process allows sulfurization of the active metal components of the catalyst due to the presence of hydrogen in situ, at the required stoichimetric or other.
In European Patent No. 84,400,234, at least one sulfurizing agent with the general formula R.sub.1 --S.sub.(n') --R.sub.2 i.e., an organic polysulfide, is used to incorporate sulfur in a pores of the new or regenerated catalyst.
In the polysulfide with the general formula: and R.sub.1 --S.sub.(n') --R.sub.2, n' is an integral number ranging from 3 to 20, R.sub.1 and R.sub.2, which are identical or different from one another, represent organic radicals, each comprising 1 to 150 atoms of carbon per molecule, these radicals being selected from the group consisting of saturate, unsaturate, linear or branched, or naphthenic alkyl radicals aryl radicals, alkylaryl radicals and arylalkyl radicals, possibly containing at least one heteroatom. R.sub.2 can also optionally be a hydrogen atom.
Preferred polysulfides include ditertiododecylpolysulfide (n=5), wherein R.sub.1 and R.sub.2 both are dodecyl radicals, and ditertiononylpolysulfide, (n=5), wherein R.sub.1 and R.sub.2 are nonyl radicals (TPS 37 is produced by ELF).